<span class="clickable collection-sort"
      [ngClass]="{active: isSorted()}"
      (click)="sort()">
  <i *ngIf="isSorted()"
     class="fa fa-angle-up"
     [class.fa-angle-up]="collection.sortOrder === 'ASC' && comparator"
     [class.fa-angle-down]="collection.sortOrder === 'DESC' && comparator"
     aria-hidden="true"></i>
  {{label}}
</span>
